Even if you could see the IP (or some hash of it), there are always some spammers who go to extreme lengths to spam/harass, especially if they are intentionally targeting a channel.
I’ve run #wow on quakenet since WoW was still in beta and over the years we’ve had to at times use some pretty extreme measures to prevent the spammers that such a well known game attracts, and sadly there’s not always an easy way to prevent some spammers without also impacting legitimate users. For example I remember a few years I think it was the German ISP t-dialin had a system that made it trivial for users to go through hundreds of IPs to spam, and so at times the whole of t-dialin had to be banned, or a blanket *.de ban.
Even if there was a system in place that let channel broadcasters/mods see an IP and let them blacklist troublesome IP’s (or IP range), it wouldn’t stop persistent spammers as it is still trivial to get around. The spammer problem is something I hope Twitch is in the process of dealing with on their end, and I would hope recruiting some more experienced global mods/admins to deal with the issue (as I’ve seen global mods in huge channels that seem to sit by and do nothing to try to prevent it, unless they are powerless?).